1. Field of the Invention
The present invention relates to an overhead travelling crane system and, more particularly, to an overhead travelling crane system for driving a wheel rim.
2. Description of the Related Art
When a wheel rim is worked, the ear on one side of the wheel rim is clamped. Then, the ear on the other side of the wheel rim proceeds an inner and outer diameter working process (OP1). Then, the ear on the other side of the wheel rim is clamped after the OP1 is finished, and proceeds a disk surface working process (OP2). Then, the wheel rim is turned through a determined angle to proceed an air nozzle working process (OP3). Finally, the working procedure of the wheel rim is accomplished after the OP3 is finished. An overhead travelling crane system is used to carry, clamp and turn the wheel rim which has a heavy weight. A conventional overhead travelling crane system comprises an oil cylinder to lift and lower the wheel rim. However, the oil cylinder easily fails due to a frequent displacement of the wheel rim. In addition, the oil cylinder has a high cost of maintenance.